The present invention relates in general to a system and method for constraining microcomponents in a desirable manner, and in specific to a method and system for handling microcomponents that are totally released from a substrate in a manner that enables such microcomponents to be constrained to a base and unconstrained as desired.
Extraordinary advances are being made in micromechanical devices and microelectronic devices. Further, advances are being made in MicroElectroMechanical System (xe2x80x9cMEMSxe2x80x9d) devices, which comprise integrated micromechanical and microelectronic devices. The terms xe2x80x9cmicrocomponentxe2x80x9d and xe2x80x9cmicrodevicexe2x80x9d will be used herein generically to encompass microelectronic components, micromechanical components, as well as MEMS components. Traditionally, microcomponents are fabricated on a substrate in a manner such that the microcomponents are fixed or anchored to such substrate. Thus, microcomponents are traditionally not totally released from a substrate, but instead are fixed to the substrate.
An example of a typical fabrication process of the prior art is described in conjunction with FIGS. 1A-1E. Turning to FIG. 1A, a substrate (e.g., a wafer) 102 is provided, on which a first layer of sacrificial release layer (e.g., silicon oxide) 106 is deposited. As shown in FIG. 1B, the sacrificial release layer 106 is then etched (or patterned) into a desired shape. Typically, the sacrificial release layer 106 is etched to form an opening therein to the substrate 102, as shown in FIG. 1B. Thereafter, a layer of polysilicon (xe2x80x9cP1xe2x80x9d) 108 is deposited, as shown in FIG. 1C. Where the sacrificial release layer 106 was etched to form an opening to substrate 102, P1 108 fills such opening to form an anchor 104, which anchors the structure to substrate 102. As shown in FIG. 1D, the P1 layer 108 is then etched (or patterned) into a desired shape. Further polysilicon and sacrificial release layers may be added in a similar manner. Additionally, electrical conducting layers (e.g., gold) and electrical insulating layers (e.g., silicon nitride) may be added to produce a microcomponent having electrical conductivity and/or insulation. Finally, the sacrificial release layers, 106 for example, may be released by exposing such sacrificial release layers to a releasing agent, such as hydrofluoric acid (HF), resulting in a microcomponent that is fixed (or xe2x80x9canchoredxe2x80x9d) to the wafer, as shown in FIG. 1E.
In most respects it has been beneficial for a microcomponent to be fixed (or anchored) to its substrate, in the prior art. For example, if the microcomponent is not anchored to the substrate during the release of the sacrificial layers (e.g., layer 106), the microcomponent may become lost, mis-positioned, or otherwise difficult to handle. For instance, to release the sacrificial layers, a substrate is commonly placed in an HF bath. Thus, if the microcomponent were not anchored to the substrate, the microcomponent might float around in the HF bath. Furthermore, the microcomponent may become mis-positioned (e.g., positioned in an undesirable manner on the substrate) and/or be difficult to handle in the HF bath. However, many situations arise in which it is desirable to totally release a microcomponent from its substrate. For example, it may be desirable to release a microcomponent from its substrate in order to perform assembly operations with such released microcomponent, e.g., assemble the released microcomponent to other microcomponents. Accordingly, relatively crude techniques have been developed in the prior art for removing a microcomponent from its substrate anchoring.
An example of a first prior art technique is described in conjunction with FIG. 2. As shown, microcomponent 208 may be anchored to wafer 202 with anchor 204. As described in the exemplary fabrication process above, the anchor 204 may be a polysilicon layer and the microcomponent 208 may comprise any number of additional layers. It can be seen that the microcomponent 208 may be removed from the wafer 202 by breaking anchor 204. However, such a crude form of removing microcomponents is often undesirable for several reasons. First, such breaking of the anchor 204 presents difficulty in defining the shape of microcomponent 208. For example, a portion of a broken anchor 204 may remain attached to microcomponent 208. Additionally, such an attached portion of a broken anchor 204 may be in the form of a spur or spike, as examples, which may be an undesirable feature to be included within microcomponent 208. Additionally, breaking of the anchor 204 may result in particles of silicon, the presence of which may be undesirable. For example, such particles may land on and interfere with the operation of microcomponent 208 or other microcomponents. Also, such particles may present a health hazard to persons that inhale such particles.
An example of a second prior art technique for removing microcomponents from a substrate is described in conjunction with FIG. 3. As shown in FIG. 3, microcomponent 308 is fixed to a tether 304 which is anchored to wafer 302 with anchor 306. As described in the exemplary fabrication process of FIGS. 1A-1E above, the anchor 306 may be a polysilicon layer and the microcomponent 308 may comprise any number of additional layers. Further, tether 304 may be in any layer that is fixed to the microcomponent 308, for example. It can be seen that the microcomponent 308 may be removed from the wafer 302 by breaking tether 304. An example of this technique is disclosed by Chris Keller in Microfabricated High Aspect Ratio Silicon Flexures, 1998. More specifically, Keller discloses a photoresist tether holding a polysilicon beam (microcomponent) to a polysilicon anchor, wherein the tether may then be broken to release the polysilicon beam component (see e.g., FIGS. 4.59 and 4.60 and discussion thereof). However, as discussed above, such a crude form of removing microcomponents is often undesirable and presents the same problems described above for breaking anchor 204 of FIG. 2. More specifically, such breaking of the tether 304 presents difficulty in defining the shape of microcomponent 308. For example, a portion of a broken tether 304 may remain attached to microcomponent 308. Additionally, such an attached portion of a broken tether 304 may be in the form of a spur or spike, as examples, which may be an undesirable feature to be included within microcomponent 308. Additionally, breaking of the tether 304 may result in particles, which may be undesirable. For example, such particles may land on and interfere with the operation of microcomponent 308 or other microcomponents, and such particles may present a health hazard to persons that inhale them.
Recent developments have allowed for fabrication of xe2x80x9ctotally releasedxe2x80x9d microcomponents (e.g., stand-alone microcomponents that are totally released from the substrate). For example, the process as disclosed in U.S. Pat. No. 4,740,410 issued to Muller et al. entitled xe2x80x9cMICROMECHANICAL ELEMENTS AND METHODS FOR THEIR FABRICATION,xe2x80x9d U.S. Pat. No. 5,660,680 issued to Chris Keller entitled xe2x80x9cMETHOD FOR FABRICATION OF HIGH VERTICAL ASPECT RATIO THIN FILM STRUCTURES,xe2x80x9d and U.S. Pat. No. 5,645,684 issued to Chris Keller entitled xe2x80x9cMULTILAYER HIGH VERTICAL ASPECT RATIO THIN FILM STRUCTURESxe2x80x9d may be utilized to fabricate totally released microcomponents. As a further example, the fabrication process disclosed in concurrently filed and commonly assigned U.S. patent application Ser. No. 09/569,330 entitled xe2x80x9cMETHOD AND SYSTEM FOR SELF-REPLICATING MANUFACTURING STATIONSxe2x80x9d allows for fabrication of totally released microcomponents. Furthermore, such fabrication process also allows for the fabrication of electrically isolated microcomponents. Additionally, other fabrication processes may be developed in the future, which may also allow for totally released microcomponents.
However, difficulties with constraining (e.g., restricting or restraining) totally released microcomponents need to be overcome. For example, when a microcomponent is totally released from its substrate during exposure to a releasing agent, such microcomponent may become lost, mis-positioned, or otherwise difficult to handle. For instance, if the microcomponent were totally released from the substrate during a HF bath, the microcomponent might float around in such HF bath. Thus, a desire exists for a system, method, and apparatus for constraining (e.g., restricting or restraining) a totally released microcomponent (e.g., to some type of base). Still a further desire exists for a system, method, and apparatus for handling totally released microcomponents. For instance, a desire exists for a system, method, and apparatus that allows for handling of totally released microcomponents in a manner that reduces the potential for such microcomponents becoming lost, mis-positioned, damaged, and/or otherwise mishandled. Given that it may often be desirable to handle totally released microcomponents in some manner, e.g., for transporting such totally released microcomponents, a desire exists for a system, method, and apparatus that aids in the handling of totally released microcomponents.
These and other objects, features and technical advantages are achieved by a system and method which constrain a microcomponent that is totally released from a substrate for handling of such totally released microcomponent. A preferred embodiment provides a system and method which constrain a totally released microcomponent to a xe2x80x9cbasexe2x80x9d. As used herein, a xe2x80x9cbasexe2x80x9d to which a totally released microcomponent may be constrained is intended to encompass a substrate, another microcomponent, a pallet, and any other surface to which it may be desirable to constrain a microcomponent. Thus, for example, in one implementation of a preferred embodiment, totally released microcomponent may be constrained to a substrate. As a further example, a preferred embodiment may be implemented to constrain a totally released microcomponent to another microcomponent. As still a further example, a most preferred embodiment provides constraining members that work to constrain a microcomponent to a substrate as such microcomponent is totally released from such substrate. Accordingly, such constraining members may aid in the removal of a microcomponent from a substrate in a manner that does not require breaking of a physical coupling between the microcomponent and the substrate (e.g., does not require breaking of a polysilicon tether or anchor to remove the microcomponent). Rather, such microcomponent may be released through exposure to a chemical releasing agent (e.g., HF), wherein the constraining members may work to preserve the location of the totally released microcomponent relative to its substrate.
As a further example, a preferred embodiment provides constraining members that are suitable for constraining a totally released microcomponent for post-fabrication handling of the microcomponent. For instance, such constraining members may preserve the totally released microcomponent with a base (e.g., its substrate) during shipment of the totally released microcomponent to a customer. Most preferably, the constraining members are implemented in a manner to aid in maintaining a desired position/orientation of the totally released microcomponent, which may enable positional assembly operations with such microcomponent.
To further aid in post-fabrication handling of totally released microcomponents, a preferred embodiment of the present invention may be implemented as a xe2x80x9cpalletxe2x80x9d having one or more microcomponents constrained thereto. For instance a pallet may be implemented which includes multiple totally released microcomponents constrained thereto. Furthermore, such a pallet may be nested, wherein a first microcomponent (or base) may be constrained to a second microcomponent (or base), which may in turn be constrained to a base (e.g., a substrate). Various microcomponents may be arranged on the pallet in a desired manner that enable positional assembly to be performed with such microcomponents, for example.
The constraining members of a most preferred embodiment may include vertical constraining members arranged to restrict vertical movement of a totally released microcomponent relative to a base. For instance, vertical constraining members may include a flap or flaps that overhang and/or underhang at least a portion of the totally released microcomponent. Furthermore, the constraining members of a most preferred embodiment may also include horizontal constraining members arranged to restrict lateral movement of a totally released microcomponent relative to a base. Moreover, in a most preferred embodiment, the constraining members may be implemented in a manner that enables the totally released microcomponent to be removed from such constraints when desired, but prevents the totally released microcomponent from inadvertently escaping such constraints. For instance, in one embodiment, the constraining members are implemented as moveable members that can be moved to unconstrain the totally released microcomponent from its base.
Thus, a preferred embodiment enables a totally released microcomponent to be constrained to a base in a manner that prevents inadvertent escape of such microcomponent from such base, but allows for one to intentionally remove the microcomponent from such constraints.